U.S. prepares to open doors on billion-dollar London embassy

LONDON (Reuters) - The United States' diplomatic team in London, custodians of one of the most significant bilateral relationships of the last 100 years, will next month move into a new home: a billion-dollar, 12-storey glass cube overlooking the River Thames.

The long-planned move falls after the election of U.S. President Donald Trump, which has placed a new strain on the "special relationship" between Britain and the United States - a broad political, cultural and military alliance forged over the last century and exercised on battlefields around the world.

Britain's closest ally will leave behind an imposing 1960 stone and concrete embassy in London's upmarket Grosvenor Square - an area known as 'Little America' during World War Two, when the square also housed the military headquarters of General Dwight D. Eisenhower.

The new site on the south bank of the river is at the heart of a huge regeneration project in a former industrial zone known as 'Nine Elms'. Set in what will become an urban park, it will host 800 staff and around 1,000 visitors each day.

The U.S. State Department ran a competition to design the new building in 2008. It described the embassy as "a physical manifestation of the long-term commitment to the special relationship between the United States and the United Kingdom."

The glass structure "gives form to core democratic values of transparency, openness and equality" a State Department briefing document said. Its $1 billion construction was wholly funded by the sale of other properties in London.

The British-U.S. relationship has been tested in recent months.

Britain's Prime Minister Theresa May was the first foreign leader to visit the White House after Trump's surprise election in November 2016. While the two leaders have committed to strengthen trade links and spoken regularly, their governments have disagreed on several issues, such as Trump's decision to decertify Iran's compliance with a multilateral nuclear deal, and his move to recognize Jerusalem as the capital of Israel.

Earlier this month, May publicly criticized Trump for reposting British far-right anti-Islam videos from his Twitter accounts. He responded with a rebuke, telling May to focus on Islamic extremism in Britain. [nL8N1O01BQ]